configure test harness to avoid too much coffee cup on mac dock :-)

test/pom.xml

@@ -236,6 +236,10 @@ THE SOFTWARE.
                       <name>buildDirectory</name>
                       <value>${project.build.directory}</value>
                     </property>
+                    <property>
+                      <name>java.awt.headless</name>
+                      <value>true</value>
+                    </property>
                   </systemProperties>
                 </configuration>
               </execution>